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We have investigated the mechanism of relaxivity for two magnetic resonance imaging contrast agents that both employ a cluster-nanocarrier design. The first system termed Mn8Fe4-coPS comprises the cluster Mn8Fe4O12(L)16(H2O)4 or Mn8Fe4(1) (L = carboxylate) co-polymerized with polystyrene to form ∼75 nm nanobeads. The second system termed Mn3Bpy-PAm used the cluster Mn3(O2CCH3)6(Bpy)2 or Mn3Bpy (2) where Bpy = 2,2′-bipyridine, entrapped in ∼180 nm polyacrylamide nanobeads. Here, we investigate the rate of water exchange of the two clusters, and corresponding cluster-nanocarriers, in order to elucidate the mechanism of relaxivity in the cluster-nanocarrier. Swift-Connick analysis of O-17 NMR was used to determine the water exchange rates of the clusters and cluster-nanocarriers. We found distinct differences in the water exchange rate between Mn8Fe4and Mn8Fe4-coPS, and we utilized these differences to elucidate the nanobead structure. Using the transverse relaxivity from O-17 NMR line widths, we were able to determine the hydration state of the Mn3Bpy (2) cluster as well as Mn3Bpy-PAm. Using these hydration states in the Swift-Connick analysis of O-17 NMR, we found the water exchange rate to be extremely close in value for the cluster Mn3Bpy and cluster-nanocarrier Mn3Bpy-PAm.

Numerous researchers around the globe are focusing their efforts toward the development of renewable energy sources. Among them are devices that harvest sun light and use it to split water into molecular hydrogen and oxygen. Thereby water oxidation is believed to be one of the bottlenecks that needs to be overcome through the development of appropriate catalysts. An in-depth understanding of the fundamental properties of those catalysts is crucial in order to improve them further or to design novel catalysts with high catalytic activity and stability. Theoretical studies offer a great opportunity, to elucidate the structure and dynamics of the catalyst, the catalytic mechanism, and the properties of potential intermediates. In this chapter, we describe our recent efforts for advanced modeling of catalysis and how the combined effort of experimental and computational work can lead to a better understanding of the catalysts at hand and development of new catalysts. Thereby we focus on two families of catalysts studied by our group. First we introduce tetranuclear Co(II)-based water oxidation catalysts featuring a cubane core as found in the oxygen evolving complex of nature's photosystem II. Afterward, we discuss selected mononuclear Ru(II)-based water oxidation catalysts.

Numerous researchers around the globe are focusing their efforts toward the development of renewable energy sources. Among them are devices that harvest sun light and use it to split water into molecular hydrogen and oxygen. Thereby water oxidation is believed to be one of the bottlenecks that needs to be overcome through the development of appropriate catalysts. An in-depth understanding of the fundamental properties of those catalysts is crucial in order to improve them further or to design novel catalysts with high catalytic activity and stability. Theoretical studies offer a great opportunity, to elucidate the structure and dynamics of the catalyst, the catalytic mechanism, and the properties of potential intermediates. In this chapter, we describe our recent efforts for advanced modeling of catalysis and how the combined effort of experimental and computational work can lead to a better understanding of the catalysts at hand and development of new catalysts. Thereby we focus on two families of catalysts studied by our group. First we introduce tetranuclear Co(II)-based water oxidation catalysts featuring a cubane core as found in the oxygen evolving complex of nature's photosystem II. Afterward, we discuss selected mononuclear Ru(II)-based water oxidation catalysts.

Insights from Imaging in Bioinorganic Chemistry continues a long-running series that describes recent advances in scientific research, in particular, in the field of inorganic chemistry. Several highly regarded experts, mostly from academe, contribute on specific topics. The series editor chooses a sub-field within inorganic chemistry as the theme and focus of the volume, extending invitations to experts for their contributions; the current theme is insights from metal ion imaging in bioinorganic and medicinal chemistry.Contains concise, informative accounts that are not too highly specialized, therefore appealing to a wide range of scientists and health professionalsPresents contributions from highly qualified international expertsProvides intrinsic scientific interest and applications, including important issues relating to the diagnosis and therapeutics that are relevant to public health

Insights from Imaging in Bioinorganic Chemistry continues a long-running series that describes recent advances in scientific research, in particular, in the field of inorganic chemistry. Several highly regarded experts, mostly from academe, contribute on specific topics. The series editor chooses a sub-field within inorganic chemistry as the theme and focus of the volume, extending invitations to experts for their contributions; the current theme is insights from metal ion imaging in bioinorganic and medicinal chemistry.Contains concise, informative accounts that are not too highly specialized, therefore appealing to a wide range of scientists and health professionalsPresents contributions from highly qualified international expertsProvides intrinsic scientific interest and applications, including important issues relating to the diagnosis and therapeutics that are relevant to public health

Insights from Imaging in Bioinorganic Chemistry continues a long-running series that describes recent advances in scientific research, in particular, in the field of inorganic chemistry. Several highly regarded experts, mostly from academe, contribute on specific topics. The series editor chooses a sub-field within inorganic chemistry as the theme and focus of the volume, extending invitations to experts for their contributions; the current theme is insights from metal ion imaging in bioinorganic and medicinal chemistry.Contains concise, informative accounts that are not too highly specialized, therefore appealing to a wide range of scientists and health professionalsPresents contributions from highly qualified international expertsProvides intrinsic scientific interest and applications, including important issues relating to the diagnosis and therapeutics that are relevant to public health

The introduction of high power ultrasound (i.e., sound energy with frequencies in the range 15 kHz to 1 MHz) into liquid reaction mixtures is known to cause a variety of chemical transformations [ 1-47]. The chemical effects of ultrasound on chemical reactions were first reported by Richards and Loomis [48] in 1927. This early report was followed by a detailed investigation of the catalytic effect of ultrasonic irradiation on the autoxidation of the iodide ion [49]. Since then, the application of ultrasound as a catalyst in chemical synthesis has become an important field of research as described by Mason in Chapter 8.